Stage, containing a Series of Dramatic Criticism; Lectures on the English Poets (reprinted Philadelphia, 1818); Political Essays, with Sketches of Public Characters; Lectures on the English Comic Writers; Table Talk; a Letter to W. Gifford; an English Grammar, &c. Two or three years before his death, he published a life of Napoleon Bonaparte (4 vols., 8vo., 1828 et seq.). He was also one of the writers in the Supplement to the Encyclopædia Britannica. The editor of the London Literary Gazette, in noticing his death, says, "Though differing widely from him in most of his opinions, we must allow that he produced much which did credit to his abilities. It was his asperities which rendered his per formances generally unpalatable to us, and the dislike was not removed by an officious and affected style. Yet there were bright parts, and of these alone we would now cherish the remembrance, as of a clever but unamiable man, who was, as he himself tells us, 'at feud with the world,' and who, consequently, treated the world with ill will, if not malice, which the world requited with something of resentment and scorn."

HEAD; the part of the animal body which contains the brain and the higher organs of sense. In many animals, it is connected with the trunk, by the neck, and is more or less movable; in some animals, however, it is immovable, and is merely a prolongation of the trunk. The head in animals is more distinct in proportion as the brain is more fully developed as the centre of the nervous system. It is entirely wanting in the lowest classes of animals, which, therefore, from the intestinal worms downward, form a third class, in the system of Latreille, under the name of acephala (headless animals), while those provided with heads are divided into two classes, the vertebral animals, having distinct and proper heads, and the cephalidia, having small and less distinctly formed heads. In this part the mouth (q. v.), as the opening of the œsophagus, is always situated. In the second class of animals, in which the head is less distinct, that part of the body which is provided with the mouth, may be called the head end. In the vertebral animals (mammalia, birds, reptiles and fish), the head has a bony basis (cartilaginous only in the cartilaginous fishes). In fishes, the bones of the head are not united with each other; and the formation of the separate bones is various. In cartilaginous fishes, the head is more or less oblong and angu 18

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lar; in osseous fishes, it is less flattened, and composed of a considerable number of bones connected in various ways; in all fishes, the cavity of the brain is very small and oblong. Equally various is the formation of the head in the different classes of reptiles. In general, the head is composed of few bones, and morė rounded in proportion as the brain is more developed. In birds, the bones of the head are more closely formed into one whole, constituting a skull more or less round, which contains the brain, and to the fore part of which the beak is attached. But the head is most perfect in the mammalia, and resembles the human head more nearly as the animal approaches more nearly to man. In general, the human head may be considered as the standard, which may be traced, with gradual deviations, through the different classes, until it entirely ceases in the lower orders of animals. Nowhere is its proper office, to serve for the reception of the nervous system, so distinct as in the human head; the cavity of the skull containing the principal organ of sensitive life-the brain; as the great cavities of the trunk containthe chest, the organs of irritable life (the heart and lungs), and the abdominal cavity, the organs of the reproductive life (the organs of digestion and generation). The superiority of the head over the other two parts just mentioned, appears also front the circumstances, that whilst it is preeminently the seat of the nervous system, it also contains organs essential for functions of the irritable and reproductive system; as the inspiration and expiration of the air are effected through the nostrils and mouth, and the entrance of food into the abdominal cavity, as well as the preparation of it for digestion, by mastication and the production of saliva, is effected by the mouth; and these organs appear more prominent, in the heads of animals, as their sensitive system sinks lower in the scale. It must not be forgotten, that the head also contains the tongue, an organ not only important in respect to nourishment, but also communicating the desires and thoughts, until it becomes in man the organ of oral intercourse, of language, and of the finest music-singing. The human head, and, more or less, the head of other animals, is divided into two chief parts, the skull (see Skull) and the face (q. v) The importance of the head as the noblest part of the animal system, has occasioned it to be used metaphorically, in all languages, to denote that which is chief. (See Ear, Eye.) HEARING. (See Ear.)

HEARNE, Samuel; an English traveller in the service of the Hudson's bay company. He was employed, in 1769, to explore the north-western part of the American continent. The narrative of his researches, published after his death, which occurred in 1792, is entitled a Journey from the Prince of Wales's Fort, in Hudson's Bay, to the Northern Ocean (1795, 4to.).

HEART; a hollow, muscular organ, the function of which is to maintain the circulation of the blood, and which is of different formations in different animals. The organs of circulation are the heart, the arteries, the veins (see Blood Vessels), and the capillary vessels. The blood (q. v.) is divided into the arterial blood and the venous blood. The object of the circulation (see Harvey) is to carry the venous blood, which has returned from the body, into the lungs, where, by the influence of the air, it is converted into arterial blood, which is then again sent out into the system, to nourish it and repair its losses. The heart in men, quadrupeds and birds (see Animal) is composed of four cavities, two auricles and two ventricles (thence called double). It is enveloped in a membrane called the pericardium, situated toward the left of the cavity of the chest, between the lungs, and resting on the diaphragm. Its form is that of a cone flattened on its inferior and superior faces, the latter formed principally by the right, the former by the left auricle and ventricle. The right auricle communicates with the right ventricle, besides which there are in it three openings, that of the vena cava inferior, that of the vena cava superior, and that of the coronary vein. The communication between this auricle and ventricle is closed by a valve when the heart contracts. The right or pulmonary ventricle communicates with the pulmonary artery, which is provided with three valves. When these valves are brought together, they interrupt the communication between the ventricle and the artery. The left auricle communicates with the left ventricle, and contains also the orifices of the four pulmonary veins. The left ventricle, besides the communication with the left auricle, contains the orifice of the aorta. (q. v.) The ventricles are divided from each other by a fleshy wall, called the septum cordis. The valves at the openings of the arteries are called semilunar; that at the orifice of the right auricle, tricuspid; that at the orifice of the left auricle, mitral; and that at the orifice of the vena cava inferior, the Eustachian valve. The heart is formed of a firm, thick, muscular tissue, composed of fibres,

interlacing with each other. It is also composed of nerves, membranes and vessels. The coronary arteries arise from the aorta, and are distributed on the heart. The coronary veins return the blood of the heart into the right auricle. The arteries (from the Greek anọ, air, and Tnpeis, to preserve, because they were thought to contain air) are the vessels which serve to carry the blood from the heart to all parts of the body. They terminate in the capillary vessels (q. v.)—a series of extremely minute vessels, which pass over into the veins. The veins are the channels by which the blood passes back from the body into the auricles of the heart. The blood which is returned from the veins is black, and is called venous; that which leaves the heart is red, and is called arterial. The red blood, possessing nourishing and vital properties, rises in the capillary system of the lungs, flows into the pulmonary veins, thence is received into the left cavities of the heart, from which it passes into the aorta, and is transmitted to all parts of the body, to the capillary system. It there loses two degrees of temperature, and undergoes other changes, by the loss of some of its elements in the important functions of nutrition, calorification, and the secretions. It is now become black, passes through the veins, from the extremities of the body towards the heart, receives the chyle and the lymph, and is emptied into the right cavities of that organ, which returns it, through the pulmonary artery, to the capillary vessels of the lungs, where it is subjected to the influence of the air, resumes the qualities of red or arterial blood, and is ready for a new course. Having thus described the route of the blood through the different parts of the system, we will now explain the mechanism of the sanguineous system. blood contained in the two vena cava is poured into the right auricle, which contracts, and thus forces the fluid to escape; but the vena cava superior opposes to its passage the column of blood which it contains, the other veins are closed by valves, and it must therefore pass into the right ventricle. The ventricle then contracts, and the tricuspid valve closing the passage through which the liquid entered, it is forced forward into the pulmonary artery, which contracts, and its orifice being closed by the semilunar valve, propels the blood still forward into the capillary system of the lungs, whence it passes into the pulmonary veins, which pour it into the left auricle by their four orifices. The contraction of the auricle impels it

The

into the left ventricle, by which it is, in the same manner, driven forward into the aorta (the mitral valve preventing its return into the auricle), and thence into the general circulation as above described. The two auricles contract and dilate simultaneously with each other, as do also the two ventricles. The dilatation is called diastole; the contraction, systole. It is difficult to determine what quantity of blood the heart projects at each systole. It is generally estimated at two ounces. The causes of the alternate contraction and dilatation of the heart are not less difficult to decide. They are entirely involuntary and dependent on the nervous system. The force of its contractions is likewise unknown. The systole of the ventricles is the cause of the motion of the blood in the arteries, which also, dilate with each wave driven into them by the motion of the heart. (See Pulse.) By what means the blood is made to penetrate the thousand windings of the capillary system, and what causes impel it to flow back through the veins, are yet subjects of dispute among physiologists. The time in which a drop of blood completes its circle of motion, has been differently estimated, at from 24 hours to 2 minutes. Among the lower orders of animals, the organization of the circulating system is very different. The infusoria, polypi and intestinal worms have no distinct vessels, much less a heart; the echinodermata have distinct organs of circulation, but no part resembling a heart. Insects have a small cylindrical vessel, running along the back, which is rather the rudiment of a vascular system, than of a heart. The first traces of a heart are found in some worms, in which some expansions are perceptible in a part of the vessel which runs the whole length of the body. In the spiders, lateral vessels are given off from the main vessel, and a pulsation is perceptible. The crustacea have a heart composed of one fleshy ventricle. In the mollusca, the heart appears completely formed; some of them have three cavities. The four classes of vertebral animals have red blood, but fishes and reptiles have only what is called a single heart, that is, composed of one auricle and one ventricle.

HEART'S-EASE. (See Violet.)

HEAT. (See Caloric, and Animal Heat.) HEATH (erica); a beautiful genus of shrubby plants, admired on account of their lasting verdure, their light foliage, and the elegance of their flowers. Their leaves are simple and entire; their flowers oval, cylindrical, or even swelled at the

base, resembling those of vaccinium and andromeda, to which genera they are allied; the corolla is four-cleft; the stamens eight, terminated by anthers, which are usually notched or bi-aristate at the summit. More than 250 species are known, 12 or 15 of which inhabit Europe, and have small flowers, whilst all the remainder are natives of South Africa, many of them bearing large and brilliantly-colored flowers, forming one of the most characteristic genera of that singular region,where, however, according to Burchell, their range is very limited, the whole tribe totally disappearing on approaching the tropic from the cape. They are very difficult of cultivation. The common heath of Europe (E. vulgaris), a low shrub, often covers, exclusively, extensive tracts of barren land, and is used for some purposes of domestic economy: mixed with oak bark, it is employed in tanning; and, also, when tender, for fodder. Notwithstanding the depth to which the roots penetrate, and the difficulty of exterminating it, such has been the progress of agriculture in Great Britain, that a considerable portion of these tracts have been reclaimed.

HEATHFIELD, lord. (See Eliott.)

HEAVEN, in a physical sense, is the azure vault which spreads above us like a hollow hemisphere, and appears to rest on the limits of the horizon. Modern astronomy has taught us, that this blue vault is, in fact, the immeasurable space in which our earth, the sun, and all the planets, with the countless host of fixed stars, revolve. The blue color of the heavens is, according to Nollet, an effect of the light of the sun and stars. According to this explanation, the boundless fields of unillumined space must, like all things else in the absence of light, appear black; but the light of the celestial bodies, which is reflected by the earth to the air, and thence again to the earth, occasions the blue color. Saussure derives the blue color, indeed, from the reflected light, but attributes the reflection not to the air, but to the vapors which it contains. He supports his opinion in this way: that if this were owing to the reflection of light from the air, glaciers and mountains covered with snow, seen at a distance of 70 to 90 miles, would appear blue. That the rays of light are, in fact, reflected by the vapors in the atmosphere, appears also from this circumstance, that the heavens, seen from a high mountain, appear of a much darker blue than when seen from a plain; and even from this last situation, the blue is very different at different times, and ap

pears dark in proportion to the purity of the atmosphere. Saussure, on the basis of these observations, has invented an apparatus, called a cyanometer, in order to determine the quantity of vapor in the atmosphere, from the degree of blueness in the color of the sky.-Heaven, in the ancient astronomy, denoted an orb or circular region of the ethereal heaven. The ancient astronomers assumed as many different heavens as they observed different celestial motions. These they supposed to be all solid, thinking they could not otherwise sustain the bodies fixed in them; and spherical, that being the most proper form for motion. Thus they have seven heavens for the seven planets, the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn. The eighth was that of the fixed stars, which was particularly denominated the firmament. Ptolemy adds a ninth heaven, which he calls the primum mobile. After him, two crystalline heavens were added by Alphonso, king of Castile, to account for some irregularities in the motions of the other heavens; and, lastly, an empyrean heaven was drawn over the whole, for the residence of the Deity; which made, in all, twelve heavens. But others admitted many more heavens, according as their different views and hypotheses required: Eudoxus supposed 23; Regiomontanus, 33; Aristotle, 47; and Fracaster no less than 70.

HEAVY SPAR. (See Barytes, Sulphate of.) HEBE; the goddess of youth, and the. cup-bearer on Olympus, a daughter of Jupiter and Juno, who gave her as a wife to Hercules, in reward of his achievements. In the arts, she is represented with the cup, in which she presents the nectar, under the figure of a charming young girl, her dress adorned with roses, and wearing a wreath of flowers. An eagle often stands beside her (as at the side of Ganymede), which she is caressing.

HEBER, Reginald, DD., bishop of Calcutta, was born April 21, 1783, at Malpas, in Cheshire, and, in 1800, was sent to Brazen-nose college, Oxford. In 1802, he obtained a university prize for a copy of Latin hexameters; and the following year he greatly distinguished himself by another prize poem-Palestine-in English. He was elected to a fellowship in All Souls' college, and, soon after, travelled in Germany, Russia, and the Crimea, and made observations, from which many curious extracts were published in the travels of doctor E. D. Clarke. Having returned home, he published an English poem,

entitled Europe, Lines on the present War (1809). About the same time, he was presented to the family living of Hodnet, and he married Amelia, daughter of the reverend W. Shipley, dean of St.Asaph. For several years subsequently, he devoted himself, with great assiduity, to his duties as a parochial priest. In 1822 appeared his life of Jeremy Taylor, with a review of his writings. On the death of bishop Middleton, he was offered the see of Calcutta, which he accepted, and, June 16, 1823, embarked for the East Indies. On Ascension day, 1824, bishop Heber held his first visitation, in the cathedral of Calcutta; and he subsequently made progresses through various parts of his very extensive diocese, consecrating churches, and taking the appropriate steps for extending the knowledge of Christianity among the Hindoos. Having taken a journey in the discharge of his episcopal duty, he arrived at Tirutchinopoli, April 1, 1826; and, on the next day, while bathing, he was seized with an apoplectic fit, which terminated his existence. Since the death of this prelate, has been published, a Narrative of a Journey through the Upper Provinces of India, from Calcutta to Bombay (2 vols., 4to., new edition, 3 vols., 8vo.). His widow has also published his biogra phy (2 vols., 4to., London, 1830).

HEBERT, James René, notorious during the French revolution, was born at Alençon, in the department of the Orne, about 1755. When yet very young, he went to Paris, where he supported himself by very dishonorable methods. Employed as a checque-taker at the Théâtre des Variétés, he was dismissed for dishonesty; after which he lived with a physician, whom he ungratefully robbed. At the beginning of the French revolution, Lemaire published a journal supporting constitutional principles, under the title Père Duchêne, which was distributed in the streets. The Jacobins soon established another paper, also called Père Duchêne, and Hébert became editor. It owed its success to the warmth and virulence with which he advocated the popular cause, and abused the court and the monarchy. August 10, 1792, he became one of the members of the municipality of Paris, which contributed to the massacre in the prisons in the following September. Hébert was soon after nominated attorney-general of the commune, and employed all his influence in forwarding a project to establish the authority of the commune on the ruins of the national representation. The Hebertists rejected the advances of the Orleans party,